Make sure the Serial port is enabled in BIOS?
I've seen integrated-chipset-provided serial ports be disabled in
BIOS and still be probed and in used by the OS. The ghost ports
would then work depending on how the OS serviced them.
I've also seen multiple ports configured on the same resources.
[RC]

It's enabled and it does work. I can log into the PIX, but when I
say "write terminal" and it starts spitting out the configuration
then that's when I get those error messages and it stops receiving
data from the device.

Now, sharing the same resources is another thing which I haven't
checked for. I'll take a look when I reboot the machine. Should be
3F8 and 2F8 right?